1. Field of the Invention
The present invention relates to a flash memory, and more particularly, to a method for erasing flash blocks based on back-bias, and a structure thereof.
2. Description of the Background Art
While Dynamic Random Access Memory (DRAM) or Static RAM (SRAM) lose data when power turned off, flash memory has the advantage of Read Only Memory (ROM) that maintains stored data even when the power is off and the advantage of RAM that can input and output data. Thus, flash memory is called non-volatile memory.
Since non-volatile memory can be highly integrated just as DRAM and it has an excellent data preservation property, it can be used as an auxiliary memory in a system and it has a wide range of applications, such as data storage including personal electronic communication devices, digital cameras, Moving Picture Experts Group Audio Level 3 (MP3) players, and memory cards which require mobility and portability.
When the flash device is formed by using a silicon-on-insulator (SOI) substrate, there are advantages such as devices can be easily isolated, the area of each flash device can be reduced, and a short-channel effect caused by reduced channel length of each flash device can be reduced.
Particularly, SOI technology which makes it possible to manufacture an ultra fine transistor having a double gate, a tri-gate, or a gate array, such as FinFET, is essential for the manufacturing of tera-bit flash memory devices going beyond sub-40 nm level.
However, since the SOI substrate does not have a silicon substrate connected to a channel, there is a shortcoming that it cannot use conventional Fowler-Nordheim (F-N) tunneling which collectively erases data through block erasion and sector erasion by supplying high-voltage to a well.